Scientists have long known that breathing in air sullied by car emissions and other pollutants could trigger asthma attacks. However, the new study is the first to quantify air pollution’s impact on asthma cases around the globe.

“Millions of people worldwide have to go to emergency rooms for asthma attacks every year because they are breathing dirty air,” said Susan C. Anenberg, PhD, MS, lead author of the study and an Associate Professor of Environmental and Occupational Health at the George Washington University Milken Institute School of Public Health (Milken Institute SPH). “Our findings suggest that policies aimed at cleaning up the air can reduce the global burden of asthma and improve respiratory health around the world.”

Asthma is the most prevalent chronic respiratory disease worldwide, affecting about 358 million people. The new findings, published in the journal Environmental Health Perspectives , suggests car emissions and other types of pollution may be a significant source of serious asthma attacks.

The mask changes colour dynamically according to real time measurements of air pollution levels and air quility index standards for PM 2.5. Credit: Greg McNevin / Global Call for Climate Action

54 countries

Anenberg and her team first looked at emergency room visits for asthma in 54 countries and Hong Kong, and then combined that information with epidemiological exposure-response relationships and global pollution levels derived from satellites orbiting the earth.

The international, multi-institutional research team includes scientists from the George Washington University Milken Institute School of Public Health, the University of Colorado Boulder, the Stockholm Environment Institute, the National Aeronautics and Space Administration (NASA), the Japan Agency for Marine-Earth Science and Technology, the Norwegian Meteorological Institute, and others.

The new research suggests that:

  • Nine to 23 million annual asthma emergency room visits globally (8 to 20 percent of total global asthma ER visits) may be triggered by ozone, a pollutant generated when car, power plant and other types of emissions interact with sunlight.
  • Five to 10 million asthma emergency room visits every year (4 to 9 percent of total global asthma ER visits) were linked to fine particulate matter, small particles of pollution that can lodge deep in the lung’s airway tubes.
  • About half of the asthma emergency room visits attributed to dirty air were estimated to occur in South and East Asian countries, notably India and China.
  • Although the air in the United States is relatively clean compared to South and East Asian countries, ozone and particulate matter were estimated to contribute 8 to 21 percent and 3 to 11 percent of asthma ER visits in the United States, respectively.

“This is the first global study of the potential impacts of air pollution on serious asthma attacks that cause people to visit emergency rooms in hospitals around the world. Previous research by SEI and others have emphasized the impacts of air pollution on the number of premature deaths, but many more people are affected by poor health, through impacts of non-fatal diseases, “ said Johan Kuylenstierna, co-author and Policy Director or the Stockholm Environment Institute (SEI).

SEI’s Policy Director Johan Kuylenstierna on the global study, interview by Ylva Rylander, Press Officer at SEI.

To estimate the global levels of pollution for this study, the researchers turned to atmospheric models, ground monitors and satellites equipped with remote-sensing devices.

“The value of using satellites is that we were able to obtain a consistent measure of air pollution concentrations throughout the world,” said Daven Henze, who is the principal investigator on the project and an associate professor for the University of Colorado Boulder. “This information allowed us to link the asthma burden to air pollution even in parts of the world where ambient air quality measurements have not been available.”

Impacts in Asia

Countries like India and China may be harder hit by the asthma burden because they have large populations and tend to have fewer restrictions on factories belching smoke and other sources of pollution, which can then trigger breathing difficulties, the authors said.

“According to the study, the largest impacts of air pollution are taking place in Asia. Next week, a new report will be released outlining 25 practical actions that can really reduce air pollution in Asia. This report will be released at the first WHO conference on air pollution and health in Geneva, where aspects of air pollution and health will be discussed”, continues Johan Kuylenstierna, Policy Director at SEI.

4.1 million and 230,000 premature deaths

Approximately 95 percent of the world’s population lives in places with unsafe air. Previously, the Global Burden of Disease Study focused on quantifying the impacts of air pollution on heart disease, chronic respiratory disease, lung cancer, and lower respiratory infections – finding that fine particulate matter and ozone were associated with 4.1 million and 230,000 premature deaths in 2016, respectively.

“We know that air pollution is the leading environmental health risk factor globally,” Anenberg said. “Our results show that the range of global public health impacts from breathing dirty air are even more far reaching—and include millions of asthma attacks every year.”

To reduce the global burden caused by asthma, Anenberg suggests that policymakers aggressively target known sources of pollution such as ozone, fine particulate matter and nitrogen dioxide. She says policies that result in cleaner air might reduce not just the asthma burden but other health problems as well.

One way to reduce pollutants quickly would be to target emissions from cars, especially in big cities. Such policies would not only help people with asthma and other respiratory diseases, but it would help everyone breathe a little easier, she said.

“SEI were co-investigators and helped to initiate the research, highlighting the possibilities of performing a global study, further quantifying the air pollution impacts on health. It’s important to note that this study shows the most severe cases of asthma, so the real impact from air pollution on asthma might be even higher,” concludes Chris Malley, co-author and SEI Research Fellow at the University of York.

Read the study “Estimates of the Global Burden of Ambient PM2.5, Ozone, and NO2 on Asthma Incidence and Emergency Room Visits ” in the journal Environmental Health Perspectives.

Support for the study was provided by the NASA Health and Air Quality Applied Science Team, NASA Aura ACMAP, the Stockholm Environment Institute Low Emissions Development Pathways Initiative, and the Global Environment Research Fund of the Japan Ministry of the Environment.

Media contacts

Johan C. I. Kuylenstierna, Policy Director and co-author, Stockholm Environment Institute [email protected] +44 7968 580 557

Ylva Rylander, Press Officer, Stockholm Environment Institute
[email protected] +46 73 150 3384

Chris Malley, SEI Researcher at the University of York
[email protected]

Kathy Fackelmann, Director of Media Relations, The Milken Institute School of Public Health, The George Washington University  [email protected]